Peter U. Clark's research while affiliated with Ulster University and other places

Publications (180)

Article
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Freshwater (FW) forcing is widely identified as the dominant mechanism causing reductions of the Atlantic Meridional Overturning Circulation (AMOC), a climate tipping point that led to past abrupt millennial-scale climate changes. However, the AMOC response to FW forcing has not been rigorously assessed due to the lack of long-term AMOC observation...
Article
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The exposure of populations to sea-level rise (SLR) is a leading indicator assessing the impact of future climate change on coastal regions. SLR exposes coastal populations to a spectrum of impacts with broad spatial and temporal heterogeneity, but exposure assessments often narrowly define the spatial zone of flooding. Here we show how choice of z...
Conference Paper
A longstanding hypothesis for near-synchronous evolution of global ice sheets over ice-age cycles invokes an interhemispheric sea-level forcing whereby sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing causes grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS)....
Article
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Geodetic, seismic, and geological evidence indicates that West Antarctica is underlain by low-viscosity shallow mantle. Thus, as marine-based sectors of the West Antarctic Ice Sheet (WAIS) retreated during past interglacials, or will retreat in the future, exposed bedrock will rebound rapidly and flux meltwater out into the open ocean. Previous stu...
Article
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To date, projections of human migration induced by sea-level change (SLC) largely suggest large-scale displacement away from vulnerable coastlines. However, results from our model of Bangladesh suggest counterintuitively that people will continue to migrate toward the vulnerable coastline irrespective of the flooding amplified by future SLC under a...
Article
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Oxygen isotope speleothem records exhibit coherent variability over the pan-Asian summer monsoon (AM) region. The hydroclimatic representation of these oxygen isotope records for the AM, however, has remained poorly understood. Here, combining an isotope-enabled Earth system model in transient experiments with proxy records, we show that the widesp...
Article
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Sea-level rise due to ice loss in the Northern Hemisphere in response to insolation and greenhouse gas forcing is thought to have caused grounding-line retreat of marine-based sectors of the Antarctic Ice Sheet (AIS) (1–3). Such interhemispheric sea-level forcing may explain the synchronous evolution of global ice sheets over ice-age cycles. Recent...
Preprint
Population risk assessments of sea level rise are key to understanding the impacts of climate change on coastal communities and necessary for adaptation planning. Future sea level rise exposes coastal populations to a spectrum of risk, but assessments often define exposure narrowly, such as areas experiencing permanent inundation only. We reviewed...
Article
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Sea-level histories during the two most recent deglacial–interglacial intervals show substantial differences1,2,3 despite both periods undergoing similar changes in global mean temperature4,5 and forcing from greenhouse gases⁶. Although the last interglaciation (LIG) experienced stronger boreal summer insolation forcing than the present interglacia...
Article
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New dating of glacially-deposited rocks substantially revises our understanding of the waxing and waning of ice since the last glacial maximum. Glaciologists have long thought that moraines throughout the western United States represent ‘neoglacial’ advances about 6,000 years ago. Now, a multi-institution team led by Shaun Marcott at the University...
Article
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The main contributors to sea-level rise (oceans, glaciers, and ice sheets) respond to climate change on timescales ranging from decades to millennia. A focus on the 21st century thus fails to provide a complete picture of the consequences of anthropogenic greenhouse gas emissions on future sea-level rise and its long-term impacts. Here we identify...
Conference Paper
Global mean sealevel rose ~134 m (Lambeck et al., 2014) during the last deglaciation(~19,000 and ~8,000 years ago). A better understanding of the contribution of the Antarctic Ice Sheet (AIS) to this sea-level rise may inform projections ofglobal mean sea-level rise in a future, warming world. Earlier sea-level projections for the 21st century (IPC...
Article
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The Mid-Brunhes Transition (MBT) began ∼430ka with an increase in the amplitude of the 100kyr climate cycles of the past 800000 years. The MBT has been identified in ice-core records, which indicate interglaciations became warmer with higher atmospheric CO2 levels after the MBT, and benthic oxygen isotope (δ¹⁸O) records, which suggest that post-MBT...
Article
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A well-defined relationship between global mean sea-level rise and cumulative carbon emissions can be used to inform policy about emission limits to prevent dangerous and essentially permanent anthropogenic interference with the climate system.
Article
The last deglaciation of the Laurentide Ice Sheet in northern Quebec and Labrador led to the formation of several glacial lakes that drained into Ungava Bay and the nearby Labrador Sea. Assessing the potential impact of their drainage on ocean surface conditions and climate, however, is limited by the few existing age constraints on ice retreat and...
Article
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The Mid-Brunhes Transition (MBT) began ∼ 430 ka with an increase in the amplitude of the 100-kyr climate cycles of the past 800,000 years. The MBT has been identified in ice-core records, which indicate interglaciations became warmer with higher atmospheric CO2 levels after the MBT, and benthic oxygen isotope (δ¹⁸O) records, which suggest that post...
Article
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Changes in the Earth's magnetic field have global significance that reach from the outer core extending out to the uppermost atmosphere. Paleomagnetic records derived from sedimentary and volcanic sequences provide important insights into the geodynamo processes that govern the largest geomagnetic changes (polarity reversals), but dating uncertaint...
Article
We report 80 10Be ages on 14 moraines from Irish cirques that show a previously unrecognized signal of at least eight millennialscale fluctuations between 24.5 ± 0.7 ka and 11.0 ± 0.3 ka. Several moraine ages may be correlative with abrupt warming at the onset of the Bølling-Allerød interval (14.7 ka) and the end of the Younger Dryas interval (11.7...
Article
Although the timing of an acceleration in late-Cenozoic exhumation of southern Alaska is reasonably well constrained as beginning ∼5–∼6 Ma, the surface uplift history of this region remains poorly understood. To assess the extent of surface uplift relative to rapid exhumation, we developed a stable isotope record using the hydrogen isotope composit...
Article
Cave dripwater chemistry of Oregon Caves National Monument (OCNM) was studied, where the parameters pH, total alkalinity, calcium, magnesium, strontium, sodium and barium were analyzed at quasi-monthly intervals from 2005 to 2007. Different statistical analyses have been used to investigate the variability of the chemical parameters in the differen...
Article
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Significance The reorganizations of deep Atlantic water masses are widely thought to regulate glacial–interglacial climate changes. However, the pattern of reorganizations and their impact on ocean tracer transport remain poorly constrained by marine proxies. Our modeling study, which simulates the coevolution of water masses and oxygen isotopes du...
Article
During the late Pleistocene, multiple floods from drainage of glacial Lake Missoula further eroded a vast anastomosing network of bedrock channels, coulees, and cataracts, forming the Channeled Scabland of eastern Washington State (United States). However, the timing and exact pathways of these Missoula floods remain poorly constrained, thereby lim...
Article
Estimates of marine isotope stage (MIS) 5c and 5a global mean sea level (GMSL) based on marine terraces and coastal indicators range from 15–37 m and 9–30 m below present, respectively. Tectonic displacement and glacial isostatic adjustment (GIA) complicate efforts to refine this range. We revisit this issue using numerical predictions of post-glac...
Article
Sea surface temperatures of the past Understanding how warm intervals affected sea level in the past is vital for projecting how human activities will affect it in the future. Hoffman et al. compiled estimates of sea surface temperatures during the last interglacial period, which lasted from about 129,000 to 116,000 years ago. The global mean annua...
Article
Proxy-based indicators of past climate change show that current global climate models systematically underestimate Holocene-epoch climate variability on centennial to multi-millennial timescales, with the mismatch increasing for longer periods1, 2, 3, 4, 5. Proposed explanations for the discrepancy include ocean–atmosphere coupling that is too weak...
Article
Despite elevated summer insolation forcing during the early Holocene, global ice sheets retained nearly half of their volume from the Last Glacial Maximum, as indicated by deglacial records of global mean sea level (GMSL). Partitioning the GMSL rise among potential sources requires accurate dating of ice-sheet extent to estimate ice-sheet volume. H...
Article
The last deglaciation of the Scandinavian Ice Sheet (SIS) from to 13,000 yr ago is well-constrained by several hundred 10Be and 14C ages. The subsequent retreat history, however, is established primarily from minimum-limiting 14C ages and incomplete Baltic-Sea varve records, leaving a substantial fraction of final SIS retreat history poorly constra...
Article
A set of closely related basaltic lava flows (supersite GA-X) on Floreana Island in the Galapagos Archipelago has a published record of an excursional or transitional direction (virtual geomagnetic pole located at 153.1°E, 54.2°S with α95 = 5.0°) and a geomagnetic field strength (1.1 × 1022 Am2) that is only ~14% of the strength of the modern magne...
Article
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Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century. The focus on this 250-year window, however, obscures some of the most profound problems associated with climat...
Conference Paper
The awe-inspiring landforms of eastern Washington resulted from catastrophic outburst floods triggered by the intermittent failure of an ice dam impounding Glacial Lake Missoula. However, the magnitudes, routings, and timing for these megafloods remain largely unconstrained. Here we use surface exposure dating of high-elevation ice-rafted boulders...
Article
During the last deglaciation, sea levels rose as ice sheets retreated. This climate transition was punctuated by periods of more intense melting; the largest and most rapid of these-Meltwater Pulse 1A-occurred about 14,500 years ago, with rates of sea-level rise reaching approximately 4 m per century. Such rates of rise suggest ice-sheet instabilit...
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Considerable progress has been made in understanding the present and future regional and global sea level in the 2 years since the publication of the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change. Here, we evaluate how the new results affect the AR5’s assessment of (i) historical sea level rise, including attributio...
Article
We present 30 10Be dates on three moraines formed by small glaciers in the southern tropical Andes of Peru to determine the timing of the local Last Glacial Maximum (LGM) and subsequent deglaciation. Two terminal moraines indicate that the local LGM ended at 23.5±0.5 and 21.2±0.8 ka, or well before the end of the global LGM (20-19 ka). A recessiona...
Article
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The ongoing retreat of glaciers globally is one of the clearest manifestations of recent global warming associated with rising greenhouse gas concentrations. By comparison, the importance of greenhouse gases in driving glacier retreat during the most recent deglaciation, the last major interval of global warming, is unclear due to uncertainties in...
Article
Projections of changes in Antarctic Ice Sheet (AIS) surface mass balance indicate a negative contribution to sea level because of the expected increase in precipitation due to the higher moisture holding capacity of warmer air. Observations over the past decades, however, are unable to constrain the relation between temperature and accumulation cha...
Article
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During the last deglaciation, wetter conditions developed abruptly ~14,700 years ago in southeastern equatorial and northern Africa and continued into the Holocene. Explaining the abrupt onset and hemispheric coherence of this early African Humid Period is challenging due to opposing seasonal insolation patterns. In this work, we use a transient si...
Article
Establishing the volume of excess ice contained in the global ice sheets during the Last Glacial Maximum (LGM; ∼26,000–19,000 y ago) remains a longstanding problem in Ice Age climate dynamics. Expressed as the equivalent lowering of global mean sea level (GMSL), estimates of this value have varied from 105 (1) to 163 m (2), with many estimates sugg...
Conference Paper
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As the southern extension of the Atlantic Ocean, the Weddell Sea is a key area to study Earth’s past climate variability. It constitutes a major source of Antarctic Bottom Water formation, which influences the Atlantic Meridional Overturning Circulation. Moreover, the Weddell Gyre is an important cyclonic circulation system for water-mass communica...
Conference Paper
Currently, the lack of highly resolved Southern Ocean marine paleoclimate archives limits our understanding of the dominant feedbacks between the Antarctic ice sheets, Southern Hemisphere oceanic and atmospheric circulation, and global sea level. Two high-resolution deep-sea sites from the Scotia Sea are located in the center of Iceberg Alley and r...
Conference Paper
The deglacial evolution of the Antarctic Ice Sheet (AIS) following the Last Glacial Maximum (LGM; 26,000 – 19,000 years ago) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences. This sparseness limits our understanding of the dominant feedbacks between the AIS, Southern Hemisphe...
Conference Paper
The rate of global mean sea level rise (GMSLR) has accelerated during the last two centuries, from a rate of order tenths of mm yr-1 during the late Holocene, to about 1.7 mm yr-1 since 1901. Ocean thermal expansion and glacier melting were the dominant contributors to 20th century GMSLR, with relatively small contributions from the Greenland and A...
Data
Our understanding of the deglacial evolution of the Antarctic Ice Sheet (AIS) following the Last Glacial Maximum (26,000-19,000 years ago) is based largely on a few well-dated but temporally and geographically restricted terrestrial and shallow-marine sequences. This sparseness limits our understanding of the dominant feedbacks between the AIS, Sou...
Article
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In his News and Analysis piece reporting on the newly released fifth assessment report (AR5) by Working Group I (WGI) of the Intergovernmental Panel on Climate Change (IPCC) (“A Stronger IPCC Report,” 4 October, p. [23][1]), R. A. Kerr highlights three fundamental conclusions about climate
Article
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Most glaciers in western North America with reliable age control achieved their maximum Holocene extents during final advances of the Little Ice Age. Tiedemann Glacier, a large alpine glacier in western Canada, is an enigma because the glacier constructed lateral moraines that are up to 90 m higher, and extend 1.8 km farther downvalley, than those...
Article
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Global mean sea level has been steadily rising over the last century, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temperature to decline slowly even af...
Article
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Proxy records from Africa identify large and abrupt changes in the hydrological cycle during the last deglaciation. Explaining the complex spatial and temporal variations in African hydrology faces two challenges. First, orbital forcing of local summer insolation should have reduced precipitation in southeastern tropical Africa during the deglaciat...
Article
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Surface temperature reconstructions of the past 1500 years suggest that recent warming is unprecedented in that time. Here we provide a broader perspective by reconstructing regional and global temperature anomalies for the past 11,300 years from 73 globally distributed records. Early Holocene (10,000 to 5000 years ago) warmth is followed by ~0.7°C...
Article
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According to the Milankovitch theory, changes in summer insolation in the high-latitude Northern Hemisphere caused glacial cycles through their impact on ice-sheet mass balance. Statistical analyses of long climate records supported this theory, but they also posed a substantial challenge by showing that changes in Southern Hemisphere climate were...
Article
Full-text available
Global mean sea-level has been steadily rising over the last cen-tury, is projected to increase by the end of this century, and will continue to rise beyond the year 2100 unless the current global mean temperature trend is reversed. Inertia in the climate and global carbon system, however, causes the global mean temper-ature to decline slowly even...
Article
Full-text available
Water resources in western North America depend on winter precipitation, yet our knowledge of its sensitivity to climate change remains limited. Similarly, understanding the potential for future loss of winter snow pack requires a longer perspective on natural climate variability. Here we use stable isotopes from a speleothem in southwestern Oregon...
Article
Temperature reconstructions from the deep sea reveal how the global ice volume has varied over the past 1.5 million years.
Article
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Greenland ice-core δ(18)O-temperature reconstructions suggest a dramatic cooling during the Younger Dryas (YD; 12.9-11.7 ka), with temperatures being as cold as the earlier Oldest Dryas (OD; 18.0-14.6 ka) despite an approximately 50 ppm rise in atmospheric CO(2). Such YD cooling implies a muted Greenland climate response to atmospheric CO(2), contr...
Article
Deciphering the evolution of global climate from the end of the Last Glacial Maximum approximately 19 ka to the early Holocene 11 ka presents an outstanding opportunity for understanding the transient response of Earth’s climate system to external and internal forcings. During this interval of global warming, the decay of ice sheets caused global m...
Article
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The covariation of carbon dioxide (CO(2)) concentration and temperature in Antarctic ice-core records suggests a close link between CO(2) and climate during the Pleistocene ice ages. The role and relative importance of CO(2) in producing these climate changes remains unclear, however, in part because the ice-core deuterium record reflects local rat...
Article
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We summarize 121 14C and in-situ cosmogenic (10Be and 36Cl) ages that constrain fluctuations of the Irish Ice Sheet (IIS) since the Last Glacial Maximum (LGM) that can be linked to abrupt climate changes in the North Atlantic region. These data provide a robust means to date ice-sheet fluctuations because similar-age events can be identified from w...
Article
Deciphering the evolution of global climate from the end of the Last Glacial Maximum approximately 19 ka to the early Holocene 11 ka presents an outstanding opportunity for understanding the transient response of Earth's climate system to external and internal forcings. During this interval of global warming, the decay of ice sheets caused global m...